// CLASSES
class Shard {
  constructor(x, y, hue) {
    this.x = x;
    this.y = y;
    this.hue = hue;
    this.lightness = 50;
    this.size = 15 + Math.random() * 10;
    const angle = Math.random() * 2 * Math.PI;
    const blastSpeed = 1 + Math.random() * 6;
    this.xSpeed = Math.cos(angle) * blastSpeed;
    this.ySpeed = Math.sin(angle) * blastSpeed;
    this.target = getTarget();
    this.ttl = 100;
    this.timer = 0;
  }
  draw() {
    ctx2.fillStyle = `hsl(${this.hue}, 100%, ${this.lightness}%)`;
    ctx2.beginPath();
    ctx2.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
    ctx2.closePath();
    ctx2.fill();
  }
  update() {
    if (this.target) {
      const dx = this.target.x - this.x;
      const dy = this.target.y - this.y;
      const dist = Math.sqrt(dx * dx + dy * dy);
      const a = Math.atan2(dy, dx);
      const tx = Math.cos(a) * 5;
      const ty = Math.sin(a) * 5;
      this.size = lerp(this.size, 1.5, 0.05);

      if (dist < 5) {
        this.lightness = lerp(this.lightness, 100, 0.01);
        this.xSpeed = this.ySpeed = 0;
        this.x = lerp(this.x, this.target.x + fidelity / 2, 0.05);
        this.y = lerp(this.y, this.target.y + fidelity / 2, 0.05);
        this.timer += 1;
      } else
      if (dist < 10) {
        this.lightness = lerp(this.lightness, 100, 0.01);
        this.xSpeed = lerp(this.xSpeed, tx, 0.1);
        this.ySpeed = lerp(this.ySpeed, ty, 0.1);
        this.timer += 1;
      } else
      {
        this.xSpeed = lerp(this.xSpeed, tx, 0.02);
        this.ySpeed = lerp(this.ySpeed, ty, 0.02);
      }
    } else
    {
      this.ySpeed += 0.05;
      //this.xSpeed = lerp(this.xSpeed, 0, 0.1);
      this.size = lerp(this.size, 1, 0.05);

      if (this.y > c2.height) {
        shards.forEach((shard, idx) => {
          if (shard === this) {
            shards.splice(idx, 1);
          }
        });
      }
    }
    this.x = this.x + this.xSpeed;
    this.y = this.y + this.ySpeed;
  }}


class Rocket {
  constructor() {
    const quarterW = c2.width / 4;
    this.x = quarterW + Math.random() * (c2.width - quarterW);
    this.y = c2.height - 15;
    this.angle = Math.random() * Math.PI / 4 - Math.PI / 6;
    this.blastSpeed = 6 + Math.random() * 7;
    this.shardCount = 15 + Math.floor(Math.random() * 15);
    this.xSpeed = Math.sin(this.angle) * this.blastSpeed;
    this.ySpeed = -Math.cos(this.angle) * this.blastSpeed;
    this.hue = Math.floor(Math.random() * 360);
    this.trail = [];
  }
  draw() {
    ctx2.save();
    ctx2.translate(this.x, this.y);
    ctx2.rotate(Math.atan2(this.ySpeed, this.xSpeed) + Math.PI / 2);
    ctx2.fillStyle = `hsl(${this.hue}, 100%, 50%)`;
    ctx2.fillRect(0, 0, 5, 15);
    ctx2.restore();
  }
  update() {
    this.x = this.x + this.xSpeed;
    this.y = this.y + this.ySpeed;
    this.ySpeed += 0.1;
  }

  explode() {
    for (let i = 0; i < 70; i++) {
      shards.push(new Shard(this.x, this.y, this.hue));
    }
  }}


// INITIALIZATION
const [c1, c2, c3] = document.querySelectorAll('canvas');
const [ctx1, ctx2, ctx3] = [c1, c2, c3].map(c => c.getContext('2d'));
let fontSize = 200;
const rockets = [];
const shards = [];
const targets = [];
const fidelity = 3;
let counter = 0;
c2.width = c3.width = window.innerWidth;
c2.height = c3.height = window.innerHeight;
ctx1.fillStyle = '#000';
const text = '新年快乐';
let textWidth = 99999999;

while (textWidth > window.innerWidth) {
  ctx1.font = `900 ${fontSize--}px Arial`;
  textWidth = ctx1.measureText(text).width;
}

c1.width = textWidth;
c1.height = fontSize * 1.5;
ctx1.font = `900 ${fontSize}px Arial`;
ctx1.fillText(text, 0, fontSize);
const imgData = ctx1.getImageData(0, 0, c1.width, c1.height);
for (let i = 0, max = imgData.data.length; i < max; i += 4) {
  const alpha = imgData.data[i + 3];
  const x = Math.floor(i / 4) % imgData.width;
  const y = Math.floor(i / 4 / imgData.width);

  if (alpha && x % fidelity === 0 && y % fidelity === 0) {
    targets.push({ x, y });
  }
}

ctx3.fillStyle = '#FFF';
ctx3.shadowColor = '#FFF';
ctx3.shadowBlur = 25;

// ANIMATION LOOP
(function loop() {
  ctx2.fillStyle = "rgba(0, 0, 0, .1)";
  ctx2.fillRect(0, 0, c2.width, c2.height);
  //ctx2.clearRect(0, 0, c2.width, c2.height);
  counter += 1;

  if (counter % 15 === 0) {
    rockets.push(new Rocket());
  }
  rockets.forEach((r, i) => {
    r.draw();
    r.update();
    if (r.ySpeed > 0) {
      r.explode();
      rockets.splice(i, 1);
    }
  });

  shards.forEach((s, i) => {
    s.draw();
    s.update();

    if (s.timer >= s.ttl || s.lightness >= 99) {
      ctx3.fillRect(s.target.x, s.target.y, fidelity + 1, fidelity + 1);
      shards.splice(i, 1);
    }
  });

  requestAnimationFrame(loop);
})();

// HELPER FUNCTIONS
const lerp = (a, b, t) => Math.abs(b - a) > 0.1 ? a + t * (b - a) : b;

function getTarget() {
  if (targets.length > 0) {
    const idx = Math.floor(Math.random() * targets.length);
    let { x, y } = targets[idx];
    targets.splice(idx, 1);

    x += c2.width / 2 - textWidth / 2;
    y += c2.height / 2 - fontSize / 2;

    return { x, y };
  }
}